A Blood Test That Could Save Your Life

One of the most challenging decisions a primary care physician faces concerns preventing a heart attack in a patient who has risk factors, such as high cholesterol, and iffy symptoms like shoulder pain or shortness of breath. As a doctor, you’re uncertain whether or not you should work on the risk factors or send your patient immediately to a cardiologist for further testing.

Sometimes, however, your decision is easy because the diagnosis is obvious.

Robert, a middle aged man and former smoker with a family history of heart disease, calls to say he’s noticed pressure in his chest when he climbs stairs. The pressure stops him in his tracks, but goes away when he rests. Robert is experiencing classic angina pectoris. Because there’s a blockage inside the blood vessels that nourish his heart muscle, when he exerts himself and his heart requires more blood it can’t get enough. This is called coronary artery insufficiency. As a result of the compromised blood flow to his heart, he feels chest pain.

The cardiologist I refer him to will likely perform a myocardial perfusion scan, in which a small amount of radioactive tracer is injected into a vein in his arm while Robert undergoes an exercise stress test.The tracer will show the approximate location of the blockage.

If Robert has a positive perfusion scan—i.e., if the cardiologist can see a blockage—he’ll then likely need a coronary angiogram, using x-ray imaging and dye to show specifically where the blockage is located. If the blocked area is confined to one or two obvious locations, the cardiologist might open the artery’s channel by threading into the artery a thin tube (catheter) with a small balloon at its tip. Inflating the balloon squeezes the blockage against the artery, restoring circulation. This is called coronary angioplasty. Alternatively, the cardiologist might insert a stent, a small tube permanently placed in the blocked area of the coronary artery. The stent allows blood to flow easily to the heart muscle.

On the other hand, if the angiogram shows multiple severe blockages, the cardiologist will likely recommend coronary bypass graft surgery, using Robert’s own veins to repair his coronary arteries.

Undergoing myocardial perfusion testingis very involved and quite expensive, averaging around $1,000 not including the cardiologist’s fee. Currently, about 10 million of these procedures are performed every year, many of them not on high-risk patients like Robert, but on people with lower risk.

Mary’s risk is low
Mary, a middle-aged, mildly overweight woman, knows she’s out of shape and becomes out of breath with stair climbing. Her father died of a heart attack in his 60s, but he was obese and a cigarette smoker. Mary’s cholesterol is borderline high, as is her blood pressure. She’s seen the ads warning how heart disease in women can cause different symptoms than those in men, with fatigue, nausea, and heartburn almost as frequent as chest pain.

Mary says she’d been tired, sometimes has nausea, and takes Nexium for the heartburn. But do these add up to coronary artery insufficiency?

Her primary care physician is well aware of women’s different coronary artery disease symptoms and certainly doesn’t want Mary to have a heart attack in the weeks to come. She also knows that, according to recent data, myocardial perfusion scans are being vastly overused, especially among women with few risk factors. As a result, the number of positive test results are a fraction of the negatives.

Until recently, there was nothing available to reassure both Mary and her physician that the likelihood of heart disease was small. Then researchers invented a brilliant new blood test that examines how Mary’s genetic make-up might (or might not) place her at risk for having a heart attack.

Enter the Corus CAD
Voted one of the Top Ten Medical Breakthroughs in 2010 by Time Magazine, the Corus CAD, a “gene expression test,” takes a sample of Mary’s blood and with 86% accuracy determines whether or not Mary, with her current symptoms and mild risk factors, is indeed at risk for a heart attack.

A few days after her blood draw, Mary receives a score somewhere between 1 and 40. If her score is below 15, then, despite her symptoms, the chances of her having heart disease are extremely small. If she’s mid-range (16-27), she needs to take steps to lower her cholesterol, lose weight, and get her blood pressure down.

But if Mary’s score is over 28, her cardiologist can feel confident proceeding with further testing. If her perfusion scan is negative, lucky her! Now she can work to zero out her controllable risk factors, even though her genetic susceptibility is permanent. Her score is fixed, but she can take major steps to prevent her heart from capitulating to her genes.

The Corus CAD test explains how some people who seem to be at risk (overweight, inactive, high cholesterol) never go on to develop heart disease, while others with a clearly better health profile develop angina and need bypass surgery. We knew heart disease was genetic. We just didn’t know how to measure it.

Here are some guidelines on who should get the Corus CAD and who should not:

The test is not at all useful for people who are known to have heart disease. We don’t need genetic confirmation of what we already know. Importantly, the test does not return accurate results in people with diabetes or anyone on immunosuppressive drugs.

The test is most useful for people who have risk factors for heart disease (high cholesterol, high blood pressure, a significant family history of early heart disease) and symptoms of heart disease (like Robert’s chest pressure), especiallywhen these symptoms are the more unusual ones such as pressure in the throat/jaw/shoulder, abdominal discomfort, and nausea. Hence Corus CAD’s importance to women, who often have heart disease without the textbook symptoms.

Generally, health insurance companies cover most (but not all) of the cost of the Corus CAD. You can imagine they’d much prefer to pay for a blood test like this instead of a myocardial perfusion test, especially since the perfusion test is being ordered too frequently in low-risk patients. If you have commercial insurance or Medicare, expect your out-of-pocket cost to be no more than $150. Keep in mind, however, that your insurance company may deny payment for the test unless your medical records support evidence that you really need it (history of symptoms, documentation of risk factors).

With luck you’ll never need the Corus CAD because you’ll remain low-risk and symptom-free. You’re eating well and keeping your weight under control, exercising, and wait…you know all this.

I was all ready to sign up to have this Corus CAD blood test, until you said that results are not accurate if one has diabetes, so that rules me out. That isn’t fair, but thanks for the info anyway. Very interesting, Dr. Edelberg.

You mentioned commercial insurance above. I have BC/BS PPO that has always paid Dr. E’s tests. Will my Bc/Bs cover this test? I have been having severe pain in my left upper arm and shoulder and I would be interested in having this test. Thanks Dr. E. for always taking time to inform all of your patient’s including us online. Have a beautiful Thanksgiving to you and your family and to all of the workers there at Whole Health.

When you sign up to receive Health Tips, you can look forward to Dr. Edelberg’s smart and very current observations arriving in your in-box weekly. They’re packed with helpful information and are often slightly irreverent. One of the most common responses to the tips is “I wish my doctor talked to me like this!”

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